Shock air pressure

[Bongopony]

What is the standard air pressure for the rear shocks?. My bike seems a bit shaky after 60MPH. Could it be the back tire? (the front is new) or maybe those shocks. Im used to 2000 suzuki 1500LC which has a lower center of gravity and a soft tail design.

[redjay]

Hi. There is no standard air pressure for the rear shocks but around 20 to 30 psi usually works for a solo rider and 30 psi and up with a passenger.
Be sure to use a low pressure zero loss pump and not a garage air line or you will blow the seals in the shock.

[VulcanJeff]

I used to own a 1500 Classic and thought I had read somewhere the max psi is 38. I mentioned this to my brother one time. He owns a 1600 Nomad and said 34psi is max on his bike. Are the shocks the same between the two models? Not sure but I can't imagine them being very different. To throw a monkey wrench into the mix, the factory shop manuals for both aforementioned bikes is "do not exceed 71psi or the oil seal might blow".

I'm about 250lbs and now own a 1600 Nomad. I run around 20psi, riding solo exclusively. My brother two-ups with his wife a lot and runs 34psi.

Worth noting, you are pissing into the wind if you try airing them up with ANYTHING BUT a lossless air pump.

I'm interested in knowing what you mean by "a bit shaky" after 60mph. Describe shaky. There are a host of things that could contribute to "shaky", not just the shocks. Are the shocks properly torqued to the frame? If a higher mileage bike, maybe the swingarm bearings need repacked and torqued. What about the tire's integrity? Is it aired to spec? Is it many years old? Are there visual blemishes/defects of any sort?

[redjay]

"Shaky" could also describe worn or loose steering head bearings that causes a wobble when slowing down. A change to Allballs steering head bearings usually cures this.

[andyvh1959]

Steering head bearings too loose, or even too tight. Tire pressures being too low. Many riders run tire pressures under 30 psi which is WAY too low for a bike like a Vulcan. Front should be at least 38psi, rear 40 to 44 psi.

Another way to stabilize a bike is to add a steering head stabilizer. But this is more common on bikes with much more aggressive steering rake/trail than is common to a big cruiser style bike like the Vulcans.

[VulcanJeff]

Neck bearings, right. I was trying to keep it within the back half of the bike.

38psi front?? GULP! I tried that mid to upper 30s psi on my 1500 Classic right out of the gate. It got a new tire as soon as I bought it. It rode like it had no rubber tire on the wheel at all. Kawasaki calls for 28. I lowered the pressure to 32 and was happy with the handling and cushiness. Ditto on my 1600 Nomad. This experience is with Shinko 777 and Michelin Commander II.

[andyvh1959]

Opps, forgot I changed the wheels on Classic to 17" Mean Streak wheels with radial tires. But yes I tend to ride with higher pressures. 32 psi on the 16 bias-ply tires for a Classic sounds better.

[Sabre-t]

Originally Posted by VulcanJeff

Neck bearings, right. I was trying to keep it within the back half of the bike.

38psi front?? GULP! I tried that mid to upper 30s psi on my 1500 Classic right out of the gate. It got a new tire as soon as I bought it. It rode like it had no rubber tire on the wheel at all. Kawasaki calls for 28. I lowered the pressure to 32 and was happy with the handling and cushiness. Ditto on my 1600 Nomad. This experience is with Shinko 777 and Michelin Commander II.

Personally, I think high 30's psi on the front is too high. I run at 32 psi. Just my opinion, but I think people use air pressure to get the "right feel" for the front suspension rather than actually changing the front suspension to give the ride they want. The result is faster tire wear and a smaller contact patch. Let the tire do it's job and adjust the suspension as necessary for it to do it's job.

[mick56]

Originally Posted by redjay

Hi. There is no standard air pressure for the rear shocks but around 20 to 30 psi usually works for a solo rider and 30 psi and up with a passenger.
Be sure to use a low pressure zero loss pump and not a garage air line or you will blow the seals in the shock.

I think that is just an accepted myth mate. Just like the airbag. The air and oil are in the same chamber. Poke your valve in, and watch oil and air come out. Peg, took a pair apart, and rebuilt them. And as far as i know, he is the only bloke to post on here about it. I used a garage forecourt air line, to pump mine up to 65lb, and had no problem in 10yrs, and about 60,000m, on bumpy UK back roads,.

[Chuck A.]

I just lowered my voyager pressures down to 28f/40r. Been running 30f/42r for 3 years. Raised the front to 32 and left the rear at 42. I added a TPM to the bike Saturday and went riding a few hours. Mid 70s. After 30 minutes riding the front tire went from 31 the 36 lbs. The rear though went from 42 to 51 lbs. Maw Kaw calls for 28 front and 36 rear at 215 lbs load with 40 lbs up to 400 lbs load. Between my big azz and stuff in the bags, yeh 400+. The rear Metzler 888 180/60/16 calls for 42 max pressure. Shocks are on 28 lbs. I bought the bike with 4800 miles on it and it has always had the 40 mph shimmy even at cruise not just at decell. Guy I ran into at a filling station told me the car tire took away his wobble. My front tire wears evenly but the rear has always cupped on the outside edges but by then the center is pretty much used up. 10 to 12 thousand is about it. I do ride a little fast some times.

Voyager riders what are your best pressures for best wear.

[Sabre-t]

Originally Posted by Chuck A.

Voyager riders what are your best pressures for best wear.

I run 32F/38R with MCIIs. Very even wear on both tires, with about 19K miles on them and not yet to the wear bars.

When I got the bike, it had brand new Bridgestone Excedra tires on it. I ran the front at the recommended 28 psi for several months. During that time, I never took it on the highway. One comfortable spring day with a high in the low 80s, I took it on the highway. I checked the pressure cold with a 2nd gauge before I left to confirm the 28 psi reading on the TPMS. I had only been on the highway for about 20 minutes and the front tire was up to about 155F and 40 psi. I pulled over into a gas station, let it cool, then raised it to 32 psi. I never had another temp/pressure problem until the tire wore out. However, the months I ran at 28 psi did their damage. At 5K, the tire was worn very badly at both edges and very uneven wear, but not to the wear bars in the middle, a sure sign of running under pressure. The rear was worn to the wear bars at 5K, too.

[andyvh1959]

On motorcycles, part of tire cupping is inadequate damping in the suspension. As damping capability decreases or fails the tire flex more rapidly at the contact patch and that increased flexing on the leading edge of the tire blocks increases the cupping.

If your bike has 20,000+ miles on it and no updates have been done with the suspension it is likely in need of shock rebuilds or replacements. Fresh oil and seals in the shocks, fresh oil in the forks, maybe a preload adjustment, all improve the ride but also help to reduce tire wear. This especially applies if your bike is ridden two up and loaded. Many big v-twins, Vulcans included really don't have too much facotry rated load capacity. My 1600 Classic is only rated for 1,153 total load, 425 Frt/728 Rr, Minus the bike weight of 675 leaves 478 lbs for me, my wife and accessories/load. Well, her and I in gear = 390 lbs, leaving 88 lbs to stay within the load rating.

My BMW R1200RT, although it only weighs 570 lbs can carry over 550 lbs.

[Sabre-t]

Originally Posted by andyvh1959

On motorcycles, part of tire cupping is inadequate damping in the suspension. As damping capability decreases or fails the tire flex more rapidly at the contact patch and that increased flexing on the leading edge of the tire blocks increases the cupping.

If your bike has 20,000+ miles on it and no updates have been done with the suspension it is likely in need of shock rebuilds or replacements. Fresh oil and seals in the shocks, fresh oil in the forks, maybe a preload adjustment, all improve the ride but also help to reduce tire wear. This especially applies if your bike is ridden two up and loaded. Many big v-twins, Vulcans included really don't have too much facotry rated load capacity. My 1600 Classic is only rated for 1,153 total load, 425 Frt/728 Rr, Minus the bike weight of 675 leaves 478 lbs for me, my wife and accessories/load. Well, her and I in gear = 390 lbs, leaving 88 lbs to stay within the load rating.

My BMW R1200RT, although it only weighs 570 lbs can carry over 550 lbs.

I totally agree. Like I said earlier in the thread, people try to use air pressure to replace adjustment or maintenance to the suspension, especially on the front. I use a heavier than OEM fork oil to stiffen up the suspension and I change it every 2 - 4 years. You can really feel a difference in the front when you have new oil in the forks. And I adjust the rear shocks as needed instead of over inflating the rear tire.

[andyvh1959]

I plan to add fittings and tubing to a single air valve the fork legs of my 1600 Classic. Then I will be able to adjust the air pressure for the load on the bike and to fine tune the ride.

Another way to "adjust" the forks is to increase the oil level, which in effect reduces the air volume above the oil. Since air is compressible, as the forks compress, the air pressure increases and provides more cushion near the complete compression of the forks, kind of like a bump stop with a lot of cushion.